Customary self-supporting vehicle bodies for passenger vehicles, including the associated supporting structure, are manufactured from sheet-metal parts. The bearer members which have hollow profiles are formed by welding together two deep-drawn metal sheets or stampings. The bearer joints which form the connection of two bearers are typically formed by overlapping adjacent bearer ends and joining them at the points of contact with a weld seam or several spot welds.
The steel sheets used to construct such self-supporting vehicle bodyworks are typically shaped in a deep drawing process. While the dies used for shaping the steel sheets are relatively expensive, they do provide a cost-favorable solution for mass production since they permit large production runs. However, in view of the high investment costs for tooling, the aforesaid process is very cost-intensive for smaller production runs.
A more cost-favorable solution for small production runs is known, for example, from European Patent document EP 0 146 716. This document discloses a "space frame" type bearing structure for a passenger car body which comprises a plurality of hollow section frame members joined together by nodes or junction elements. The hollow section frame members are formed as extruded light-metal sections, typically high grade aluminum alloy, and the junction elements are formed as light-metal castings. In addition to being a more cost-favorable solution for small production runs, a light-alloy bodywork of the type disclosed in EP 0 146 716 weighs less and offers improved corrosion resistance as compare to a conventional sheet metal bodywork.
Such cast light metal junction elements typically have very complex surface configurations and include variable wall thicknesses, and/or reinforcing ribs for added stiffness as well as complex curved regions for making suitable transitions with even force distribution to the adjoining extruded hollow section frame members.
With such three-dimensionally complex structures, however, problems arise in: (1) design; (2) the production of the patterns and molds; (3) checking or tolerance verification operations; and above all; (4) the final assembly of the finished joint. The above problems are due to the fact that there is no suitable and reproducible, geometrically simple basic structure on the basis of which the design of, dimensioning, checking and adjustment or tweaking can be carried out.
For a body superstructure with narrow tolerances, it is difficult to arrange the complex-shaped junction elements in the correct position in space and to assign the connecting extruded sections to them. This is due to the unusually complicated geometry of the junction elements, which generally do not have any surfaces well suited for positionally correct mounting in an assembly device or jig. In addition, in view of the complex geometry, checking for dimensional accuracy of the parts is made difficult, thus making it necessary to accept relatively large tolerances.
It is known from French Patent Document FR 556 458 A how to releasably connect two flat components on a vehicle by a central bolt, whereby the mating surfaces of the two components have interengaging conical raised portions and correspondingly shaped depressions. The described engagement method provides an aid to adjustment and an anti-rotation safeguard. No reference, however, is made to assembly of a vehicle body from junction elements and hollow sections.
A method for the production of a vehicle body is furthermore known from German Patent Document DE 3 413 228 A1 in which the initial assembly of the vehicle body is completed without a center pillar and is fully painted. In this way, interior fittings may be introduced into the passenger compartment via the side cut-out where the center pillar would normally be disposed. Once the interior fittings have been installed, the center pillar is then inserted and connected to the vehicle body. This connection is made via a conical plug-in connection. This document, however, does not teach or suggest a three dimensional positionally correct alignment of junction elements within an assembly device.
British Patent Document GB 941 164 discloses a substructure of a vehicle body wherein a forwardly disposed transverse member is joined along each end thereof via upwardly curved bridging members to a respective one of a pair of parallel, spaced apart longitudinal frame members. The transverse member and the longitudinal members lie in parallel horizontal planes. The mating surfaces between the ends of the transverse member and the curved bridging members include upraised bosses and corresponding recesses to facilitate releasable engagement and orientation of the curved bridging member for final connection with the associated longitudinal member. This document does not teach or suggest a method for fixing a junction element in space to assist in the assembly of a plurality of adjoining frame elements thereto.